Verizon Wireless Tuesday revealed that there are five additional data tiers over and above the six tiers announced with its Share Everything plans earlier this summer.

The new top tier costs $150 a month for 20GB, a spokeswoman said.

The five new tiers, which are not detailed on Verizon’s website, join the six buckets of data unveiled in June with the Verizon Share Everything program.

The original plans range from a low of 1GB for $50 a month to 10GB for $100 a month. The data can be shared among up to ten mobile devices under the program. The other tiers above the top 10GB one listed on the website are 12GB for $110 a month, 14GB for $120 a month, 16GB for $130 a month, 18GB for $140 a month and 18GB for $150 a month, the spokeswoman told Computerworld today.

The maximum that can be purchased in advance is 20GB, she added.

The Verizon Wireless spokeswoman, Brenda Raney, said the carrier has been offering the higher tiers of data to customers since June, mainly through customer service via phone or in its stores.

The upper tiers were not posted with the original six tiers on the Verizon website in order to keep the program simple and because “the majority of customers use under 2GB a month,” Raney said. “Who would need 20GB?”

Computerworld contacted Verizon about the upper tiers after a reader, Bryan Sherman, commented on a Computerworld story that compared Verizon’s shared data costs with those of AT&T’s coming Mobile Share plans.

Sherman noticed that Verizon’s charge of $150 for 20GB would be $50 less than AT&T’s $200 monthly charge for sharing 20GB across ten devices. Sherman derived the Verizon 20GB charge by noticing a footnote on its website that says Verizon will charge $10 a month for 2GB if a customer needs more than 10GB of data.

Raney said that customers needing more than 10GB in a given month can buy 2GB for $10 by logging into their account on the tab “My Verizon” at VerizonWireless.com.

However, she said that capability only applies to purchasing one allotment of 2GB of extra data per month, not multiple ones.

To get to 20GB—or 12GB, 14GB, 16GB or 18GB—a customer must arrange with customer service to get that allotment as part of a monthly plan, Raney said.

Verizon also has an overage charge of $15 per 1GB of data for exceeding a plan’s allowance. Theoretically, if a customer purchased 10GB for $100, then used an added 10GB without arranging for it in advance, the overage would be $150, for a total monthly data charge of $250.

While Raney, Sherman, and others questioned whether many users would need 20GB in a month, that amount is relatively easy to hit if shared across ten users.

As an example, a single cellular download of a high definition full-length movie can use up more than 3GB of data—downloading the movie for seven users would exceed the 20GB limit.

AT&T evidently saw the probability of ten users wanting 20GB by including it as the top tier in its published Mobile Share plan, coming August 23.

Both the Verizon and AT&T plans fix a monthly cost per device in addition to the shared data cost.